1. Technical Field
The present invention relates generally to devices for providing a vehicle with an auxiliary source of heat and more particularly to an auxiliary heating device which is packaged with another one of the vehicle accessory devices.
2. Discussion
In conventionally configured vehicles, the heating system is typically configured in a manner which extracts heat from the coolant circulated through a water-cooled engine to heat the air that is forced into the vehicle passenger compartment. Some engines, however, such as diesel and lean-burn engines, reject so little heat that it is not possible to extract a sufficient amount of heat from the engine coolant to heat the passenger compartment at a desired rate.
To overcome this problem, many vehicle manufacturers employ an auxiliary heating device, such as a conventional viscous heater. Viscous heaters generate heat by applying a shearing force against a fluid. In response to the shearing force, the fluid is heated and this heat is in turn extracted to heat the air forced into the vehicle passenger compartment. Despite the apparent success of such viscous heaters, several drawbacks have been noted.
One significant drawback concerns the ability with which these devices may be integrated into a vehicle. Frequently, the engine compartment of modern vehicles lacks sufficient space to integrate a viscous heater in a conventional manner, necessitating the use of additional idler wheels to configure the drive belt in a desired manner and/or bracket assemblies to mount the viscous pump to the engine. The use of additional idler wheels and brackets adds significant cost to the vehicle which must be passed along to the vehicle consumer.
U.S. Pat. No. 5,743,467 to Ban et al. issued Apr. 28, 1998, which is hereby incorporated by reference as if fully set forth herein, addresses this concern by coupling a viscous heater to a vehicle accessory, such as an alternator or a power steering pump. This configuration, however, presents several other disadvantages in that the viscous pump and vehicle accessory are continuously driven from a single input shaft. Consequently, additional torque is required from the vehicle starter or starters to start the vehicle engine to overcome the additional torque created as a result of the shearing force applied by the viscous heater. Another disadvantage of this configuration is that the viscous heater is run continuously, even when auxiliary heat is not required. Operation of the viscous heater in this manner reduces the fuel economy of the vehicle.
Consequently, there remains a need in the art for an auxiliary heating device which may be easily integrated into a vehicle and controlled in a manner so as to minimize its effect on the fuel economy of the vehicle.